To manufacture integrated circuit (IC) devices, photolithography is typically used. Photolithography produces a three-dimensional pattern on a surface of a substrate using a light-sensitive photoresist material and controlled exposure to light. Generally, the resist is applied on the substrate surface as a polymer solution. The resist is then baked, which drives out the solvent. Next, the resist is exposed to controlled light. The light passes through a mask that defines the desired pattern. The pattern is transferred to the resist, and the resist is used to transfer the pattern to the underlying substrate. In this way, layers can be built one on top of another to form the desired IC device.
Patterned conductive material on one level is typically electrically insulated from patterned conductive material on another level by a layer of dielectric material. FIG. 1 illustrates an IC substrate 100 having a first patterned metal layer 104 and a second patterned metal layer 108 according to the prior art. The first patterned metal layer 104 is formed on a substrate 102. A dielectric layer 106 is formed over the first patterned metal layer 104 and separates the second patterned metal layer 108 from the first patterned metal layer 104. The second patterned metal layer 108 is formed on the dielectric material 106. The space 110 between the two patterned metal layers is occupied only by dielectric material 106, taking up space and adding unwanted thickness to the IC substrate 100.
FIGS. 2A-2J illustrate a method that is typically used to form patterned metal layers on a substrate. In FIG. 2A, a substrate 200 with a first metal layer 202 formed on the substrate 200 is provided. In FIG. 2B, a photoresist layer 204 is formed on top of the first metal layer 202, and in FIG. 2C, the photoresist layer 204 is patterned to include various openings that expose portions of the first metal layer 202 to subsequent etch. In FIG. 2D, the first metal layer 202 is patterned using the photoresist layer 204. In FIG. 2E, the photoresist layer 204 is removed, leaving the first patterned metal layer 202. In FIG. 2F, a dielectric layer 206 is formed over the first patterned metal layer 202. In FIG. 2G, a photoresist layer 208 is formed on top of the dielectric layer 206. In FIG. 2H, the photoresist layer 208 is patterned and etched to expose portions of the dielectric layer 206. In FIG. 2I, a second metal 210 is deposited on the exposed portions of the dielectric layer 206, and in FIG. 2I, the photoresist layer 208 is removed, leaving the second patterned metal layer 210 and the first patterned metal layer 202, with the dielectric layer 206 separating the two metal layers.
Advances in semiconductor IC design, processing, and packaging technologies have resulted in increases in the number and density of features in a substrate. Nonetheless, the size of portable electronic systems such as portable computers, cell phones, PDAs, etc. continues to shrink despite the addition of new features and functions. New features and functionalities, such as digital cameras and camcorders, global positioning systems, and removable memory cards are continually being integrated into modern portable and/or high density electronic systems. It is therefore desirable to decrease the thickness of the components within portable electronic systems to provide size reduction as well as additional space to add new components.
Accordingly, there is a need in the art for thin, low profile substrates.